Some substances will change their chemical structure under the irradiation of a certain wavelength of light, which will change the absorption spectrum, thereby changing the color of the substance: these substances will be restored to the original under the irradiation of different wavelengths of light or the action of heat. Color; other substances cannot restore the original color. This reversible or irreversible discoloration and decolorization phenomenon is called "photochromic" phenomenon. These materials are called photochromic materials. This kind of material is used for the color changing mirror in daily life.

    The use of photochromic materials to make printing inks is photochromic inks, which have a wide range of applications and applications.

    When photochromic materials are applied to these inks, the problems of adhesives, solvents, additives, etc. should be considered at the same time, because the internal substances of these inks will cause the photochromic materials to react. The following describes the application of photochromic materials in screen printing inks.

Photochromic screen printing inks can be water-based, oil-based, plastic inks, etc.

    The manufacturing method of this kind of ink is to first dissolve the photochromic pigment with a solvent to form a microformed pigment capsule, and add a dynamic agent to the dissolved pigment according to different uses; or dissolve the photochromic pigment into a monomer and pulverize This type of polymer ultrafine particles (approximately 1 to 5 pm) are powders, and these powders are used as pigments. Compared with microcapsule inks, the ink made by this method has a 10 times light resistance. These powders can be used as pigments in water-based inks, oil-based inks, plastic inks, and all additives.

1. Photochromic water-based screen printing ink

The characteristics of this water-based ink are: 1 can quickly develop color in the sun, and can be restored to a colorless state in a short time after shading (different colors are different. After 2 to 3 minutes, yellow can be completed in an instant); 2 Good dispersion performance, uniform color development can be obtained: 3 Good color rendering and friction fastness; 4 This water-based ink is a liquid type ink: 5 Good storage stability and easy operation.

2. Photochromic oil-based screen printing ink

Oil-based inks are mainly used for surface printing on plastic films and metal plates. This ink is printed on a screen for 100 to 200 days. There are many resins used in adhesives: acrylic, epoxy resin, urethane, cyclized rubber modified resin, silicone modified resin and so on. As solvents, there are esters, ketones, etc., as well as mineral turpentine and petroleum. Adding photochromic materials to these adhesives composed of resin and solvent can adjust the viscosity of screen printing ink appropriately to make oil-based screen printing ink.

3. Photochromic plastic screen printing ink

This plastic ink is made of ultra-fine vinyl acetate copolymer powder (about 1 pn) with DOP plasticizer to expand the particles to make silk screen ink.